The present invention relates to the weighing of long, heavy vehicles such as highway trucks, and more particularly, to platform scales useful in determining the weight of such vehicles.
Long, concrete scales, or weighbridges have previously been built using a pad of prestressed concrete with steel underframe crossbeams at or near the 2 ends. Similarly weighbridges have been built utilizing a series of previously prestressed weighbridge pads, arranged end for end in a manner not unlike the building of a series of short scales arranged adjacent to each other, each almost having separate steel underframe crossbeams at or near its ends. Weighbridges have also been made by butting concrete panels against each other end to end and prestressing the entire assembly by post-tensioning cables running continuously through the assembly, suitably supporting steel crossbeams are positioned across the panels at the ends and at the intermediate butting hinge joints. In the prior art embodiments described, the steel crossbeams rest on load cells and in operation the load cell signals are summed thereby determining the weight on the structure. A major problem with such scale designs is the requirement of steel crossbeams at the support points. Steel is relatively expensive and requires protective maintenance on a regular basis to avoid corrosion. In addition, a further difficulty is that for a low profile construction any of the above proposals would require a large number of costly load cells.
A weighbridge according to the present invention minimizes the amount of exposed steel allowing the use of expensive protective coatings or even the substitutions of stainless steel without sacrificing economic competitiveness. Furthermore, the utilization of a long slab as a continuous beam facilitates the use of a reduced number of supports and, in turn, a substantial reduction in the number of costly load cells required. There are two factors in the design of the present device that permit the reduction of the number of supports, and load cells with a minimum slab thickness. These are: (1) a continuous structure which allows the use of a significant cantilever at each end of the weighbridge, thereby reducing the intermediate spans for a given weighbridge length and (2) a continuity of structure which inherently reduces the midspan moment for all intermediate spans by about 50% over what the moment would have been had the spans been simply supported. Typically prior art devices have spans that are simply supported.